Non-volatile static random access memory (nvSRAM) is a type of semiconductor memory that is capable of storing the data, even when the memory is not powered. Referring to FIG. 1, a conventional nvSRAM 100 comprises a plurality of nvSRAM cells 102, each including an SRAM portion 104 for storing data during normal operations when the memory is powered, and a non-volatile memory portion 106 including a number of charge storing or memory transistors with a charge storage layer capable of retaining data after power has been removed and, once power is restored, reprogramming the SRAM portion. The nvSRAM 100 further comprises control circuitry or a controller 108 to control erase, program, and recall or read operations of the non-volatile memory portion 106 to copy data from the SRAM portion 104 to the non-volatile memory portion.
The copying of data from the SRAM portion 104 to the non-volatile memory portion 106 on a drop or loss of power (VCC) to the nvSRAM is referred to as an autostore operation. One problem with conventional nvSRAMs and methods of operating or driving the same is that a large, external electrolytic capacitor 110 is required during an autostore operation to provide power to erase and then program the non-volatile memory portion 106 of the cells to store data from the SRAM portion 104. The external capacitor 110 increases the size, complexity and cost of the nvSRAM 100.
Accordingly, there is a need for non-volatile memory and method of operating the same that reduces the size of or eliminates entirely the need for an external capacitor to power the memory the during an autostore operation.